Dosage forms stabilized with surfactants are often rendered unstable by electrolytes even at low salt or acid concentrations: suspensions are flocculated or their sediments cake, emulsions and ointments separate, and insoluble drugs solubilized in micelles precipitate. Dosage forms stabilized with nonionic surfactants are more resistant to electrolytes than those stabilized with ionic surfactants because of different stabilization mechanisms, because nonionic surfactants require higher electrolyte concentrations for salting out while anionic surfactants are incompatible with polyvalent cations. When dosage forms stabilized with nonionic surfactants are broken down by electrolytes, salting out via dehydration of the surfactant molecules is the major cause. Our systematic investigations on the effects of electrolytes on nonionic surfactants have shown that only salts of sodium, potassium and ammonium salt out nonionic surfactants, reducing their solubility. Salts of polyvalent cations and acids actually salt in nonionic surfactants by complex formation with the ether groups of the latter. The well established breakdown of dosage forms stabilized with nonionic surfactants by added electrolytes is ascribed to the fact that sodium and potassium salts were usually involved - the few cations that are not complexed by nonionic surfactants and therefore salt them out. We propose to study the effects of salts of di- and trivalent cations and acids on dosage forms stabilized with nonionic surfactants and to determine whether salting in of the surfactants by these electrolytes results in improved stability. This involves measuring the extent of flocculation and caking in suspensions and of phase separation in emulsions, ointments and micellar solutions as a function of the concentration of added electrolytes, using colloid-chemical techniques. The stoichiometry and thermodynamic parameters of the complexation of salting-in electrolytes by nonionic surfactants will be determined.